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Continued concern with herbicide resistance weeds

Waterhemp in an Iowa soybean field (photo courtesy Iowa State University)

Waterhemp in an Iowa soybean field (photo courtesy Iowa State University)

Herbicide-resistant weeds continue to be a growing concern across the Midwest.

Iowa State University Extension crops specialist Joel DeJong says part of the problem is a lack of new weed-killing chemistries. He says the last new family of herbicides was introduced in the 1980’s.

“It’s kind of scary because we’ve had lots of new products on the market, but they’re all from the same families that already existed,” DeJong says. “Because of that, we kind of keep going back to the well and keep using the same ones—and if one works, we use it really hard.”

DeJong says glyphosate is a good example.

“Glyphosate—Roundup—worked extremely well. And it still works extremely well on most weeds,” he says. “However, there is one or two families of weeds in the state of Iowa that really have found a way to move around how glyphosate works—and so they’re becoming more resistant to it. Waterhemp is probably our biggest problem and that’s the one that most farmers have concerns about.”

DeJong says even if crop protection companies were to develop a new line of herbicides, it could be several years before they hit the marketplace.

“If one got discovered today, to pass through all the hoops and everything else to make sure it’s safe to the environment and to people and to animals, it would take at least a decade before that would become available to the market. So right now we’ve got to figure out how we’re using the tools we’ve got—how do we use them better and how do we reduce the risk of maybe developing more resistance in our weeds.”

DeJong was one of the presenters at Thursday’s ISU “Weeds Week” seminar in Cherokee, Iowa. The last Weeds Week meeting takes place Friday in Boone.

Dennis Morrice, KLEM-Le Mars, Iowa, contributed to this story.

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